I'm building a new deck and can't decide on the size of the joists. The deck will be 18 feet wide and 12 feet deep, and will be built with pressure treated pine. The joists will be 16 inches O.C. and the span will be approximately 11.5 feet from the house to the support posts. Because of an existing structure below the deck, I can't place the support posts closer to the house. I understand that 2x8 joists at 16 O.C. can span a little more than 12 feet, but I'm thinking I should go with 2x10 joists at 16 O.C. What do you think, should I go with the 2x10 joists for this deck? I would hate to go too small and regret the decision later. Thanks in advance!